This invention relates to personal health monitors and more particularly to improvements for a personal health monitor to sustain reliable operation.
A personal health monitor is a device used to measure and record one or more clinical parameters of a patient for later review by the patient's physician or other health care provider. The personal health monitor may be used in a hospital or clinical setting as an adjunct to existing care. However, the personal health monitor may also be used by the patient in his own home. When used by a patient in his own home, the patient operates the personal health monitor to record certain of his own clinical parameters. The personal health monitor, therefore, may be used by the patient who has a condition requiring monitoring of one or more clinical parameters but who otherwise does not require the level of care such as provided by a hospital. In such a circumstance, the personal health monitor provides potential savings in medical costs involved with a hospital stay. A personal health monitor of the type considered herein is described more fully in U.S. Pat. No. 4,803,625.
The personal health monitor may include one or more test components, or sensors, a programmable computer such a general purpose personal computer, and an interface connecting the sensors with the personal computer. In the above referenced patent, the programmable computer is a laptop personal computer having a display screen, a keyboard, CPU (central processing unit), disk drive, and a means for connecting to the interface such as through a port, expansion slot, bus, or other means.
A program on the computer affords an interative, user-friendly way for the patient to interact with the personal health monitor to measure one or more clinical parameters. For purposes of this application, clinical parameters include physiological parameters, (such as vital signs like ECG, blood pressure, temperature, and weight), medication compliance and volunteered patient replies. The program can be specifically tailored to the patient's individual needs.
With the sensors a patient can measure one or more specific physiological parameters. The interface connects to the sensors and converts the signals from the sensors for storage as data by the personal computer.
In accordance with the testing regime established by the patient's physician, the personal health monitor may be used on a specific schedule to conduct sessions to measure certain of the patient's clinical parameters following instructions provided by the personal health monitor. In the embodiment described in the above referenced patent, the personal health monitor includes a personal computer with a display screen portion that can provide instructions for conducting a session in which clinical parameters are determined. For example, the program on the personal computer can provide instructions for measuring a patient's blood pressure or ECG. In addition, the personal health monitor can also present the patient with a series of questions about his health and prompt the patient for responses. For example, the patient can be asked to volunteer replies in response to a structured series of questions (e.g., "Do you have a fever? " followed by "If so, is your fever continuous or intermittent? "). The personal health monitor can be programmed to sound a reminder to initiate a testing session and record whether the patient adheres to the established schedule.
The personal health monitor can be used to give the patient instructions for taking medicines and provide the patient with reminders to take medications. Moreover, the personal health monitor can allow a physician to readily modify a medication schedule. For example, based upon the physiological parameters gathered by the personal health monitor and reviewed by a patient's physician, the physician may decide to alter the medication.
As described in the above referenced patent, the personal health monitor may include means for data storage so that the clinical parameters measured can be stored as data. The personal computer may include a modem so that the data can be transmitted to a central station. The data transmission can be done automatically by a program on the personal computer. An alternative is to convey the data on a diskette or other storage medium to the central station. The physician or other health care provider can then obtain the information from the central station either by calling, downloading or other means of communication. Alternately, a health care provider may be able to access the personal health monitor directly.
An advantage of the personal health monitor is that a high level of patient surveillance can be provided, even with the patient outside of a hospital or other expensive facility. Thus, the personal health monitor has the capability of lowering health care costs while at the same time maintaining or even improving the level of patient surveillance. Additional benefits include being able to return a patient to his home environment sooner and also providing a means for involving the patient in his own health program.
A concern with using a personal health monitor for home use involves providing a safe yet reliable power supply. For example, various sensors such as ECG sensors pose a potential risk of electric shock to a patient while the personal health monitor is directly connected to ordinary house current (also referred to herein as AC). To reduce or avoid the risk of any possible accidents, an isolation circuit is provided The isolation circuit can completely isolate the portion of the personal health monitor unit with which the patient interacts from the house current. The isolation circuit may be of a type, such as an opto-electric relay, that uses optical techniques to open a switch to turn off the supply of house current to the personal health monitor. During these periods, the personal health monitor can be operated from a backup battery. The backup battery may be regularly or continuously recharged by the house current during the periods of time that the isolation circuit is closed and house current is being supplied to the personal health monitor.
The same backup battery can also be used provide power to run the personal health monitor during temporary power outages. The backup battery also allows the patient to disconnect the personal health monitor for short periods of time to move it from one place to another. The battery also provides continued use of the personal health monitor in the event that the personal health monitor is accidentally disconnected from the house current.
In order that the rechargeable backup battery can be used for these purposes, it should be automatic, i.e. it should operate to provide power even in the event that the personal health monitor is unattended. A problem with unattended operation of the rechargeable battery is that with typical rechargeable batteries that are currently available, the personal health monitor will operate for only a limited time. If the personal health monitor is unattended when the AC is disconnected, it is possible that the rechargeable battery may completely run down before the power is restored. The battery may be permanently damaged or not rechargeable. It is also possible that data may be lost or destroyed.
Another concern that may occur with using a rechargeable backup battery involves the isolation circuit. An isolation circuit typically requires power to close or stay closed, i.e. to enable the path by which AC is supplied to the personal health monitor. In the absence of a supply of power, the isolation circuit will open shutting off the path for AC to reach the personal health monitor. This can be avoided by using a battery backup power supply. However, if the backup battery also runs down, there would be no power to keep the isolation circuit closed. Thus the isolation circuit would open. Then even if the AC is restored, the isolation circuit would be open and would prevent the AC from reaching the personal health monitor.
Still another problem with using an rechargeable backup battery involves initialization. For example, it can be very important for the operation of the personal health monitor to distinguish between a condition when AC is initially supplied to the unit (for example, when it is first turned on or installed) and the condition when AC is restored to the unit after it has been disconnected for some amount of time. When the personal health monitor is first set up for use by the patient, a service person, such as a nurse, will turn the unit ON and connect it to AC (house current). During this initial installation, the personal health monitor begins operation from its backup battery which should be fully charged. In this way, it can be readily determined that the personal health monitor unit, including the backup battery, is in good operating condition. After initialization, the personal health monitor can automatically switch on a connection to the AC for the purpose of supplying current for an AC/DC converter that in turn supplies power for the operation of those personal health monitor functions that do not require isolation of the patient from AC. In addition, the personal health monitor can also use the AC for recharging the backup battery. This procedure may automatically take place when the personal health monitor unit is first turned on. However, this may not be suitable in the circumstance when AC is restored after a power outage or after the unit has been disconnected, e.g. if the personal health monitor has been disconnected for a long time, the backup battery may not have sufficient power to start up (boot) the personal computer.
Accordingly, it is an object of the present invention to preserve operation of the personal health monitor in the event of a power outage.
It is another object of the present invention to provide a means wherein an initial connection of AC to a personal health monitor can be differentiated from a reconnection to AC.
It is a further object to allow operation of the personal health monitor in the event of a power outage of a duration greater than 1-2 hours.
It is another object to reduce requirements on a battery in a personal health monitor during power outages.
It is still another object to preserve operations necessary to restart the personal health monitor system during extended periods of power outages.
It is yet still another object to provide for a staged reduction in power requirements in the event that the battery is called on the operate the personal health monitor system for an extended period of time without recharging.
It is still yet another object to conserve battery power so that minimal essential operations and data can be maintained in a personal health monitor.
It is still yet another object of the invention to prevent damage to a rechargeable battery in a personal health monitor.
It is another object of the present invention to provide a device and method for isolation of a personal health monitor from AC by both software control and hardware control.